1. Field of the Invention
The present invention relates to an image processing system, and more particularly, to an image processing apparatus for realizing panorama/waterglass functions and a method thereof.
2. Description of the Related Art
In general, if television signals having a horizontal vertical screen ratio of 4:3 are viewed on a wide television having a horizontal vertical screen ratio of 16:9, due to a visual difference caused by the difference in screen ratios, image signals appear to be stretched in the horizontal direction. Similarly, if wide television signals are viewed on a conventional television, due to a difference in screen ratios, image signals appear to be compressed in the horizontal direction. In order to remove these phenomena, panorama and waterglass functions are realized in an image processing system of each television such that the screen appears normal.
FIGS. 1A through 1C illustrate the variation in image signals when realizing a conventional panorama function. FIG. 1A illustrates conventional TV signals having a screen ratio of 4:3, FIG. 1B illustrates wide TV signals having a screen ratio of 16:9, and FIG. 1C illustrates image signals after performing a panorama function.
A panorama function is used to view conventional television signals through a wide television. If the conventional TV signals shown in FIG. 1A are viewed through a wide TV, as shown in FIG. 1B, the conventional TV signals appear to be stretched in the horizontal direction. To try and remedy this problem, a panorama function for the conventional TV signals is realized, as shown in FIG. 1C. Using the panorama function, the middle of the screen is reduced to the ratio of 4:3 so that the image signals shown in FIG. 1C appear normal. Further, the scaling ratio of the image signals at the edges of the screen increases in compensation for the reduced ratio, and thus, distortion effects increase.
In contrast, on the basis of a waterglass function, in order to prevent a phenomenon in which a screen appears to be compressed in the horizontal direction when wide TV signals are viewed on a conventional TV, the middle of the screen is increased to the ratio of 3:4, and both edges of the screen are reduced so that the screen appears normal.
However, a conventional image processing apparatus for realizing panorama and waterglass functions has drawbacks in which a memory size increases, or a method for controlling a memory becomes complicated.
FIG. 2 is a block diagram of a conventional image processing apparatus for realizing a panorama function. The conventional image processing apparatus includes an over-sampling unit 20 including an analog to digital converter (ADC) 21, an interpolating filter 22, a memory 24, a downscaler 28, and a digital-to-analog converter (DAC) 26.
The over-sampling unit 20 converts input image signals into digital signals and over-samples the converted signals at a predetermined ratio. The over-sampled image signals are interpolated by the interpolating filter 22 and the interpolated result is stored in the memory 24. Data stored in the memory 24 are input to the downscaler 28, and thus, the scaling ratio of the input image signals is reduced to a predetermined ratio at each horizontal interval. Likewise, the image processing apparatus shown in FIG. 2 uses a method for gradually reducing the scaling ratio in a state where input data are previously over-sampled.
However, the image processing apparatus shown in FIG. 2 stores data over-sampled at a predetermined ratio in the memory 24, and thus, the size of the memory increases. For example, when one line is 720 bytes, the size of the memory has a capacity corresponding to one line×2(data for luminance and color signals)×over-sampling ratio.
FIG. 3 is another block diagram of a conventional image processing apparatus for realizing panorama and waterglass functions. The conventional image processing apparatus includes an analog-to-digital converter (ADC) 300, an image memory 310, a ID flip-flop 320, a digital-to-analog converter (DAC) 330, a first phase locked loop (PLL) 340, a second PLL 350, a switching unit 360, first through third divided clock generation units 380a˜380c, and a microcomputer (MICOM) 370.
Referring to FIG. 3, the MICOM 370 generates a write enabling signal WENA for writing data into the image memory 310, and a read enabling signal RENA. The first PLL 340 generates a sampling clock signal CLK1 and a write clock signal WCK. The image processing apparatus shown in FIG. 3 generates a variable clock signal for reading data from the image memory 310 so as to satisfy the scaling ratio at each horizontal interval of an image signal. This operation is performed in the first through third divided clock generation units 380a˜380c and the switching unit 360. That is, the switching unit 360 is controlled by control of the MICOM 370, and thus, a division clock signal having an appropriate division ratio is selected as a read clock signal and applied to the image memory 310. Thus, data stored in the image memory 310 are read by a variable clock signal according to the scaling ratio.
However, in a method for varying a read clock signal, it is very difficult to realize a clock signal which is precisely switched. Further, each switched interval is stepwise classified, and the scaling ratio of a clock signal may be nonlinearly expressed. Thus, in order to obtain the linearity of the scaling ratio of a clock signal, many clock dividers are required. In this way, in the image processing apparatus shown in FIG. 3, a variable clock signal is used when data are read from the image memory 310, and thus, a method for controlling a memory becomes very complicated.